Flailing machinery for removing limbs and bark prior to introducing the wood product to a chipper for chipping the wood product into useable chips which can be used in the paper industry to make pulp has become increasingly popular in recent years. Machinery of this character, wherein flail drum systems have been employed to flail the log or tree proceeding through a flailing station are disclosed in U.S. Pat. Nos. 5,148,844 and 5,322,104, both of which are incorporated herein by reference. Flail drum systems of this type typically may have an upper rotary chain flail drum and a lower rotary chain flail drum disposed on opposite sides of a log or other wood product being moved forwardly longitudinally between the upper and lower flail drums. The upper and lower flail drums are each driven in rotation about a generally horizontal axis transverse to the path of the log. Typically, these flail drums include a central shaft, with axially spaced spacer elements thereon providing perimetrical openings through which chain supporting rods freely extend, alternately with circumferentially spaced openings through which the rods extend and which support the rods. The inner links of the chains then are supported on the rods in typically an axially progressive spiral array.
As these patents point out, and, as is well known in the art, flailing chains wear relatively rapidly and must be removed and replaced as a matter of course. When the chains are being replaced, the machine is down and cannot be used. Prior systems have focused on providing drums which can be readily disassembled in order to achieve chain replacement.
The present invention is directed to a system of improved character wherein the chain flails can be externally replaced in the sense that disassembly of the drums involved is not necessary.